In general, an electronic component is disposed on a printed circuit board inside an electronic device by reflowing (namely, reflow soldering), and the multiple electronic components are electrically connected with each other by conductive traces on the printed circuit board. During reflowing process, the printed circuit board and the electronic components are heated such that the electronic component is thermally connected with the printed circuit board by a solder pad. However, the main material of the electronic component is different from that of the printed circuit board, so the electronic component and the printed circuit board are contracted to different extents after the soldering based on the different materials. Hence, even the pin of the electronic component is precisely aligned with the solder pad of the printed circuit board before the reflowing process, the pin may be misaligned with the solder pad or the solder wire may break into two or more pieces after reflowing. When the electronic component is a rectangular shape, the pins, respectively located on the two ends along a long side of the electronic component, may not successfully solder on the solder pads.
In order to prevent the solder-joint failure, the materials with similar coefficients of thermal expansion are chosen by the related business for producing the electronic component and the printed circuit board. However, after a large quantity of experiments and tests are executed to choose the materials, the costs of the chosen materials are usually higher than others.
Therefore, it is urgent and essential to design an electronic device that the coefficients of thermal expansion of the electronic component and the printed circuit board are different and the solder-joint failure is avoided.